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Diseases of Aquatic Organisms

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DAO 70:81-92 (2006)  -  doi:10.3354/dao070081

Hepatic Calyptospora sp. (Apicomplexa) infection in a wild-born, aquarium-held clutch of juvenile arapaima Arapaima gigas (Osteoglossidae)

Christopher J. Bonar1,2,*, Sarah L. Poynton3,4, F. Yvonne Schulman4, Randall L. Rietcheck5, Michael M. Garner6

1Cleveland Metroparks Zoo, 3900 Wildlife Way, Cleveland, Ohio 44109, USA
2The Cleveland Aquarium Incorporated, 8871 Camelot Drive, Chester Township, Ohio 44026, USA
3Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, 733 North Broadway, Baltimore, Maryland 21205, USA
4Leibniz Institute of Freshwater Ecology and Inland Fisheries, Müggleseedamm 310, 12587 Berlin, Germany
5Armed Forces Institute of Pathology, Washington, DC 20306, USA
6Northwest ZooPath, 654 West Main, Monroe, Washington 98272, USA

ABSTRACT: From Manaus, Brazil, 12 juvenile arapaima Arapaima gigas were imported to the United States and sent to 2 public aquaria, 1 private hobbyist, and 1 retailer. All 12 fish became ill within 4 to 6 wk of arrival, with signs of anorexia, lethargy, depigmentation, and ascites, and subsequently died despite antibiotic and anthelminthic therapy. Gross necropsies of 7 fish revealed serosanguinous coelomic effusion in all 7 fish, and branchial monogeneosis in 3 of 6 fish. The monogeneans from 1 fish were identified as Dawestrema cycloancistrium (Ancyrocephalinae). Histologic examination of 7 fish showed a variety of lesions, principally in the liver, gills, brain and gastro-intestinal tract. Numerous coccidian oocysts replaced 15 to 33% of the liver parenchyma in 6 of 7 fish examined. Light and transmission electron microscopy revealed that each oocyst contained 4 pyriform sporocysts bearing numerous sporopodia on their tapering, posterior end; approximately 25 to 30% of the length of the sporocyst was adorned. Each sporocyst was covered by a thin, membranous veil, contained 2 sporozoites, and stained brilliant pink with the Ziehl-Neelsen acid-fast method. This morphology is consistent with that of Calyptospora sp. (Lack of fresh material precluded determination to species.) This is the first report of Calyptospora sp. in arapaima. The Calyptospora sp. infection probably contributed to the morbidity and mortality of the captive arapaima.

KEY WORDS: Arapaima gigas · Branchitis · Calyptospora · Dawestrema · Liver

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